Technical Field
The present invention relates to: a composite (hybrid) of metal oxide nanoparticles and a silsesquioxane polymer, which is used in the production of a metal oxide-containing composite cured film used in electron devices, such as a high-refractive index film or a high-dielectric film; and a method of producing the same.
Background Art
Conventionally, as cured films such as high-refractive index films and high-dielectric films that are used in electron devices, silicon films made of silicon oxide, silicon nitride or the like have been used. As a method of forming such a silicon film, a chemical vapor deposition method such as PE-CVD or a method of coating and then heat-curing a composition comprising a silicon-containing resin is employed. For the purpose of improving the physical properties or refractive index of such a cured film, studies have been conducted on dispersion of metal oxides in silicon-containing resins.
Such metal oxide-containing resins are generally produced by dispersing a metal oxide in a resin. A metal oxide can be synthesized by a variety of methods. However, it is commonly synthesized by a sol-gel method using a metal alkoxy compound as a starting material. As a solvent used in this synthesis, water or a water-alcohol mixed solvent is commonly used. Therefore, the resulting metal oxide sol has a hydrophilic hydroxy group on the surface and is often supplied in the form of an aqueous dispersion.
Accordingly, in the above-described method, a hydrophilic metal oxide is dispersed in a hydrophobic resin. However, it is difficult to uniformly disperse such a metal oxide as-is into a resin. In order to solve this problem, it has also been examined to disperse a hydrophilic group-containing metal oxide by adding a hydrophobic monomer or a resin to the surface of the metal oxide.